Beneath the glam of the Mag Mile and the towering buildings of the Loop is an underground network of delivery streets and docks. In these darkened recesses where the wind doesn't blow, the skyscrapers belch hot air and delivery trucks spew exhaust — except for one truck, a step van delivering hot dog and hamburger buns to places like the Billy Goat Tavern on Hubbard.

It idles noiselessly enough for passers-by to mistake it for being off, even with LED lights bathing the cabin.

The driver, Sean Sullivan, a 34-year veteran with Alpha Baking Co. in Chicago, shuts the gate in back, stomps up the aisle and takes his seat. He shifts the lever on the instrument panel, and the truck begins moving. There's no sound other than the stacked crates jostling with the suspension on Chicago's unleavened roads; no engine heat radiates from the firewall; no sweetly metallic taste of diesel in the air.

"The difference in driving the electric truck is it helps with concentration, the ability to hear ambulances and fire trucks more," said Sullivan, 55, who lives in Elk Grove Village. "Makes a big difference. If you're sitting right on top of the diesel engine, you get nothing but that diesel engine. And the exhaust."

Sullivan considers himself one of the lucky few who get to drive the five electric medium-grade trucks in Alpha's fleet of 52 other diesel trucks.

"We want to lessen our footprint as a company," said Paul Nosalik, logistics manager of Alpha, which makes and delivers everything from the classic poppy hot dog bun to S. Rosen's and Natural Ovens. "It's the right thing to do. We're not as dependent on foreign oil, not polluting, and we feel comfortable delivering to schools and nursing homes in the early morning."

The only sound, aside from the squeak and clank of the suspension, is the backup alert. Most deliveries to residential areas shouldn't be made until after 7 a.m., Sullivan said, but the silent electric truck enables earlier deliveries. Sullivan gets in Alpha's West Side delivery center at 2:30 a.m. and heads out at 4:30 a.m. to make 30 to 40 stops, including several in the University of Illinois at Chicago and Bridgeport areas.

"We focus on helping people deliver things," said Steve Burns, CEO of Workhorse.

The publicly traded company sold two step vans to UPS, which then ordered 18 more, then 125, then an additional 200 last year.

PLUG-IN HYBRID (PHEV) and ELECTRIC VEHICLES (BEV): The electrification of powertrains continues as automakers roll out everything from subcompact compliance cars to electrified supercars to improve efficiency and optimize power. Tesla Model 3 is just the prong on the charge cord of available plug-in vehicles. BMW, Mercedes-Benz, Ford, Volskwagen, Volvo, Hyundai have announced electrification plans for dozens of vehicles by 2020. Plug-in sales have grown 32 percent annually since 2013 (41 percent globally), and most autonomous vehicle plans are based on electric cars.

The step van is technically a plug-in hybrid vehicle with a 60 kWh battery pack giving it a 60-mile range that can be doubled with the backup 2-cylinder gas generator, same as the BMW i3 electric car.

When the delivery route is done, between 10 a.m. and noon, Sullivan plugs it into a Level 2 (240-volt) charger and the truck has full power after six to eight hours of charging. Total output for the vehicle capable of hauling 19,500 total pounds is 268 horsepower.

Tesla is in the early stages of developing an all-electric pickup truck and a full-fledged semi.

Ryder, one of the nation's largest medium-duty truck fleet management companies, agreed to an exclusive partnership with Chanje, maker of medium-grade all-electric trucks, the Los Angeles Times reported Aug. 14. Ryder customers can rent the electric trucks starting in California and expanding from there in 2018.

The use of electrified powertrains in delivery trucks is expected to grow globally to 332,000 by 2026 from 31,000 vehicles in 2016, according to a study by Navigant Research.

One big barrier of going electric is the steep initial cost.

The Workhorse plug-in step van costs about $30,000 more than a $60,000 diesel step van, Nosalik estimated. Alpha only considered it with a grant from the Chicago Area Clean Cities Coalition, a nonprofit consortium launched under the U.S. Department of Energy's Clean Cities initiative to reduce petroleum in the transportation sector.

"Originally we didn't know much about electric trucks," Nosalik said, adding that Alpha was already using alternative fuels, from 27 propane trucks to tractors powered by compressed natural gas. "We will continue with (Workhorse) without the grant money."

And they have, announcing Aug. 15 the purchase of five additional Workhorse step vans to replace five old diesels.

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It's simple economics for Alpha. After the initial outlay, the Workhorse step vans have a running cost of 4 cents a mile. The same diesel truck costs 35 cents a mile, Nosalik said.

"We focus on fleets because of the lower total cost of operations," Burns said of Workhorse's model. "Being green is just a nice byproduct."

Another nice byproduct is driver satisfaction.

"My truck is the Breadman," Sullivan said, petting the dash with affection. The gate was signed by the original Breadman, onetime Blackhawk phenom Artemi Panarin.

During his deliveries, we talk in a normal voice, above the squeaking suspension and jostling crates. He pulls into a place like Al's Beef, is out of the truck for three to five minutes, which would be idling diesel fuel otherwise, and is on to the next stop. Stop-and-go driving is best served by electric vehicles.

There are limitations to the truck. There's no air conditioning because the frequency of deliveries, sometimes within the same block, means nothing would stay cold anyway. Highway speed is limited to 67 mph for efficiency. When the battery dips below a 50 percent charge, Alpha programmed the generator to kick on.

Sullivan seems more charmed than bothered by the trade-offs. He'll keep driving the Breadman as long as he's driving. "I foresee these trucks on routes everywhere real soon."